ACTIVITY OF BULBAR RESPIRATORY NEURONS DURING FICTIVE COUGHING AND SWALLOWING IN THE DECEREBRATE CAT

1. The behaviour of medullary respiratory neurons was studied during f ictive coughing and swallowing evoked by electrical stimulation of the superior laryngeal nerve (SLN) in decerebrate, paralysed and artifici ally ventilated cats. Fictive coughing, swallowing and respiration wer e monitored by recording activities of the phrenic, hypoglossal and ab dominal nerves. 2. Extracellular recordings were made from respiratory neurons in the ventral respiratory group (VRG) and in the Botzinger c omplex (BOT). The neuronal types analysed included decrementing inspir atory neurons (I-DEC), augmenting expiratory neurons (E-AUG) and decre menting expiratory neurons (E-DEC) from the BOT area, and augmenting i nspiratory neurons (I-AUG) and augmenting expiratory neurons (E-AUG) f rom the VRG area. 3. During fictire coughing, all the inspiratory and expiratory neurons mere active during the inspiratory and expiratory p hases of coughing, respectively. The firing of both I-DEC and I-AUG ne urons was increased and prolonged in association with the augmented in spiratory activity of the phrenic nerve. The activity of E-AUG neurons of the VRG did not parallel the abdominal nerve activity, suggesting the existence of additional neurons which participate in the generatio n of abdominal nerve activity during fictive coughing. 4. During ficti ve swallowing, half of I-DEC neurons fired transiently at the onset of hypoglossal bursts associated with swallowing; the firing was suppres sed during the rest of the hypoglossal bursts. Other I-DEC neurons mer e silent during hypoglossal bursts. Some I-AUG neurons fired during th e initial half of hypoglossal bursts, and others were silent. The brie f phrenic activitS accompanying the swallowing might have originated f rom this activity in I-AUG neurons, The discharges of all E-AUG neuron s (BOT and VRG) and the majority of E-DEC BOT neurons were suppressed during swallowing. 5 We conclude that these five types of respiratory neurons of the BOT and VRG are involved in the generation of the spati otemporally organized activity of coughing and swallowing, and that at least a part of the neuronal network for respiration is shared by net works for these non-respiratory activities.